A vehicle that includes a direct injection gasoline engine may include a GPF. The GPF may store carbonaceous soot produced by the direct injection engine. From time to time, the GPF may be regenerated to reduce exhaust back pressure and the amount of soot stored in the GPF. The GPF may be regenerated by operating the GPF above a threshold temperature and providing excess oxygen to the GPF. The excess oxygen may help to combust soot stored in the GPF, thereby reducing the amount of soot stored in the GPF. The excess oxygen may be provided by combusting a lean air-fuel ratio in the engine or via providing air to the GPF. However, vehicle emissions may increase if the engine is operated with a lean air-fuel ratio or if air is provided to the vehicle's exhaust gas after treatment system. Therefore, it may be desirable to increase the possibility of operating the vehicle during conditions where oxygen may be provided to the GPF without increasing vehicle emissions.
The inventors herein have recognized the above-mentioned issue and have developed a vehicle system, comprising: a spark ignited engine; an exhaust system coupled to the spark ignited engine, the exhaust system including a particulate filter; and a controller, the controller including executable instructions stored in non-transitory memory to operate the spark ignited engine and adjust one or more automatic vehicle speed controller parameters in response to an amount of soot stored in a particulate filter greater than a threshold amount.
By adjusting one or more vehicle speed controller parameters in response to an amount of soot stored in a particulate filter, it may be possible to provide the technical result of regenerating a particulate filter more frequently than if the vehicle operates with a same group of vehicle speed controller parameters during automatic vehicle speed control. In particular, base vehicle speed controller control limits may be populated with values that maintain vehicle speed at a desired vehicle speed plus or minus a predetermined vehicle speed. Further, the vehicle speed controller may include modest gains to maintain vehicle speed within an upper vehicle speed limit and a lower vehicle speed limit. However, if a large amount of soot is stored in the particulate filter, the vehicle speed controller gains may be increased and the desired vehicle speed range may be increased to induce more frequent entry into deceleration fuel shut-off so that the particulate filter may be passively regenerated while operating the vehicle in a speed control mode.
For example, when an amount of soot stored in a particulate filter is less than a first threshold, a desired vehicle speed may be 100 KPH. The controller may have an upper vehicle speed boundary of 103 KPH and a lower vehicle speed boundary of 97 KPH. If vehicle speed exceeds 103 KPH, engine torque may be gradually reduced so as to not make rapid engine torque changes. Similarly, if vehicle speed is less than 97 KPH, engine torque may be gradually increased so as to provide a gradual increase in engine torque and vehicle speed. In this way, vehicle speed may be controlled to desired vehicle speed without inducing larger engine torque changes when the amount of soot stored in a particulate filter is less than a first threshold.
On the other hand, if the amount of soot stored in the particulate filter is greater than a threshold, vehicle speed controller parameters may be adjusted to increase the possibility of entering a deceleration fuel shut-off mode. For example, the controller upper vehicle speed limit may be adjusted to 108 KPH and a lower vehicle speed limit may be adjusted to 93 KPH for a desired vehicle speed of 100 KPH. Further, the vehicle speed controller gains may be made more aggressive (e.g., increased) in response to the amount of soot stored within the particulate filter.
The vehicle speed control upper vehicle speed limit may be increased and a lower vehicle speed limit may be decreased in response to the amount of soot stored in the particulate filter being greater than a threshold to allow requested engine torque to approach zero for a longer period of time if the vehicle encounters a negative grade. Further, the vehicle speed controller gains may be increased in response to the amount of soot stored in the particulate filter being greater than the threshold so that larger and longer engine torque reductions may be provided to increase the possibility of entering deceleration fuel shut-off mode.
The present description may provide several advantages. In particular, the approach may increase the propensity for larger engine torque changes while operating a vehicle in an automatic speed control mode so that the vehicle has a greater possibility of entering deceleration fuel shut-off mode. Further, the approach may reduce the possibility of the particulate filter being actively regenerated, thereby increasing vehicle fuel efficiency. Further still, the approach may increase the possibility of the particulate filter being ready for regeneration during a deceleration fuel shut-off mode.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.